The present invention is directed to phase change (hot melt) ink compositions. More specifically, the present invention is directed to phase change ink compositions suitable for use in ink jet printing processes, including piezoelectric ink jet printing processes, acoustic ink jet printing processes, and the like. One embodiment of the present invention is directed to a phase change ink composition comprising (a) a nonpolymeric ester compound ink vehicle having a melting point of at least about 60.degree. C.; (b) a conductivity enhancing agent; (c) a colorant; (d) an optional antioxidant, and (e) an optional UV absorber.
Acoustic ink jet printing processes are known. In acoustic ink jet printing processes, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (i.e., liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. These principles have been applied to prior ink jet and acoustic printing proposals. For example, K. A. Krause, "Focusing Ink Jet Head," IBM Technical Disclosure Bulletin, Vol. 16, No. 4, September 1973, pp. 1168-1170, the disclosure of which is totally incorporated herein by reference, describes an ink jet in which an acoustic beam emanating from a concave surface and confined by a conical aperture was used to propel ink droplets out through a small ejection orifice. Acoustic ink printers typically comprise one or more acoustic radiators for illuminating the free surface of a pool of liquid ink with respective acoustic beams. Each of these beams usually is brought to focus at or near the surface of the reservoir (i.e., the liquid/air interface). Furthermore, printing conventionally is performed by independently modulating the excitation of the acoustic radiators in accordance with the input data samples for the image that is to be printed. This modulation enables the radiation pressure which each of the beams exerts against the free ink surface to make brief, controlled excursions to a sufficiently high pressure level for overcoming the restraining force of surface tension. That, in turn, causes individual droplets of ink to be ejected from the free ink surface on demand at an adequate velocity to cause them to deposit in an image configuration on a nearby recording medium. The acoustic beam may be intensity modulated or focused/defocused to control the ejection timing, or an external source may be used to extract droplets from the acoustically excited liquid on the surface of the pool on demand. Regardless of the timing mechanism employed, the size of the ejected droplets is determined by the waist diameter of the focused acoustic beam. Acoustic ink printing is attractive because it does not require the nozzles or the small ejection orifices which have caused many of the reliability and pixel placement accuracy problems that conventional drop on demand and continuous stream ink jet printers have suffered. The size of the ejection orifice is a critical design parameter of an ink jet because it determines the size of the droplets of ink that the jet ejects. As a result, the size of the ejection orifice cannot be increased, without sacrificing resolution. Acoustic printing has increased intrinsic reliability because there are no nozzles to clog. As will be appreciated, the elimination of the clogged nozzle failure mode is especially relevant to the reliability of large arrays of ink ejectors, such as page width arrays comprising several thousand separate ejectors. Furthermore, small ejection orifices are avoided, so acoustic printing can be performed with a greater variety of inks than conventional ink jet printing, including inks having higher viscosities and inks containing pigments and other particulate components. It has been found that acoustic ink printers embodying printheads comprising acoustically illuminated spherical focusing lenses can print precisely positioned pixels (i.e., picture elements) at resolutions which are sufficient for high quality printing of relatively complex images. It has also been discovered that the size of the individual pixels printed by such a printer can be varied over a significant range during operation, thereby accommodating, for example, the printing of variably shaded images. Furthermore, the known droplet ejector technology can be adapted to a variety of printhead configurations, including (1) single ejector embodiments for raster scan printing, (2) matrix configured ejector arrays for matrix printing, and (3) several different types of pagewidth ejector arrays, ranging from single row, sparse arrays for hybrid forms of parallel/serial printing to multiple row staggered arrays with individual ejectors for each of the pixel positions or addresses within a pagewidth image field (i.e., single ejector/pixel/line) for ordinary line printing. Inks suitable for acoustic ink jet printing typically are liquid at ambient temperatures (i.e., about 25.degree. C.), but in other embodiments the ink is in a solid state at ambient temperatures and provision is made for liquefying the ink by heating or any other suitable method prior to introduction of the ink into the printhead. Images of two or more colors can be generated by several methods, including by processes wherein a single printhead launches acoustic waves into pools of different colored inks. Further information regarding acoustic ink jet printing apparatus and processes is disclosed in, for example, U.S. Pat. Nos. 4,308,547, 4,697,195, 5,028,937, 5,041,849, 4,751,529, 4,751,530, 4,751,534, 4,801,953, and 4,797,693, the disclosures of each of which are totally incorporated herein by reference. The use of focused acoustic beams to eject droplets of controlled diameter and velocity from a free-liquid surface is also described in J. Appl. Phys., vol. 65, no. 9 (1 May 1989) and references therein, the disclosure of which is totally incorporated herein by reference.
In acoustic ink printing processes, the printhead produces approximately 2.2 picoliter droplets by an acoustic energy process. The ink under these conditions preferably displays a melt viscosity of from about 1 to about 25 centipoise at the jetting temperature. In addition, once the ink has been jetted onto the printing substrate, the image thus generated preferably exhibits excellent crease properties, and is nonsmearing, waterfast, of excellent transparency, and of excellent fix. The vehicle preferably displays a low melt viscosity in the acoustic head while also displaying solid like properties after being jetted onto the substrate. Since the acoustic head can tolerate temperatures typically up to about 180.degree. C., the vehicle for the ink preferably displays liquid-like properties (such as a viscosity of from about 1 to about 25 centipoise) at a temperature of from about 75 to about 180.degree. C., and solidifies or hardens after being jetted onto the substrate such that the resulting image exhibits a hardness value of from about 0.1 to about 0.5 millimeter (measured with a penetrometer according to the ASTM penetration method D1321).
Ink jet printing processes that employ inks that are solid at room temperature and liquid at elevated temperatures are known. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid inks for printing on a substrate such as paper. The ink vehicle is chosen to have a melting point above room temperature so that the ink, which is melted in the apparatus, will not be subject to evaporation or spillage during periods of nonprinting. The vehicle selected possesses a low critical temperature to permit the use of the solid ink in a thermal ink jet printer. In hot melt ink jet printing processes employing these phase change inks, the solid ink is melted by a heater in the printing apparatus and used as a liquid in a manner similar to that of conventional piezoelectric or thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the dye to remain on the surface instead of being carried into the paper by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. After the phase change ink is applied to the substrate, freezing on the substrate resolidifies the ink. When the printer employs a piezoelectric hot melt ink jet printing process, a plurality of ink jet nozzles is provided in a printhead. A piezoelectric vibrating element is located in each ink channel upstream from a nozzle so that the piezoelectric oscillations propel ink through the nozzle. After the phase change ink is applied to the substrate, freezing on the substrate resolidifies the ink.
In phase change printing processes, the ink preferably undergoes a change with temperature from a solid state to a liquid state in a desirably short period of time, typically in less than about 100 milliseconds. One advantage of phase change inks is their ability to print superior images on plain paper, since the phase change ink quickly solidifies as it cools, and, since it is primarily waxy in nature, it does not normally soak into a paper medium.
Phase change inks also preferably exhibit a high degree of transparency, generally measured in terms of haze value of the ink. Transparent, low haze inks exhibit high gloss and high optical density compared to opaque inks, although both may appear to be evenly colored.
The use of phase change inks in acoustic ink printing processes is also known. U.S. Pat. No. 4,745,419 (Quate et al.), the disclosure of which is totally incorporated herein by reference, discloses acoustic ink printers of the type having a printhead including one or more acoustic droplet ejectors for supplying focused acoustic beams. The printer comprises a carrier for transporting a generally uniformly thick film of hot melt ink across its printhead, together with a heating means for liquefying the ink as it nears the printhead. The droplet ejector or ejectors are acoustically coupled to the ink via the carrier, and their output focal plane is essentially coplanar with the free surface of the liquefied ink, thereby enabling them to eject individual droplets of ink therefrom on command. The ink, on the other hand, is moved across the printhead at a sufficiently high rate to maintain the free surface which it presents to the printhead at a substantially constant level. A variety of carriers may be employed, including thin plastic and metallic belts and webs, and the free surface of the ink may be completely exposed or it may be partially covered by a mesh or perforated layer. A separate heating element may be provided for liquefying the ink, or the lower surface of the carrier may be coated with a thin layer of electrically resistive material for liquefying the ink by localized resistive heating.
U.S. Pat. No. 5,541,627 (Quate), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for ejecting droplets from the crests of capillary waves riding on the free surface of a liquid by parametrically pumping the capillary waves with electric fields from probes located near the crests. Crest stabilizers are beneficially used to fix the spatial locations of the capillary wave crests near the probes. The probes are beneficially switchably connected to an AC voltage supply having an output that is synchronized with the crest motion. When the AC voltage is applied to the probes, the resulting electric field adds sufficient energy to the system so that the surface tension of the liquid is overcome and a droplet is ejected. The AC voltage is synchronized such that the droplet is ejected about when the electric field is near is minimum value. A plurality of droplet ejectors are arranged and the AC voltage is switchably applied so that ejected droplets form a predetermined image on a recording surface. The capillary waves can be generated on the free surface of the liquid by using acoustical energy at a level approaching the onset of droplet ejection. The liquid used with the invention must also be attracted by an electric field.
Phase change inks used in acoustic ink printing processes also preferably exhibit a low acoustic loss value, typically below about 100 decibels per millimeter. In addition, the ink vehicle preferably can fill the pores of a porous substrate, such as paper, and preferably has a melting point of from about 80 to about 120.degree. C.; this melting point, along with low acoustic loss, enables a minimization of energy consumption. When the phase change inks are used in an electric field assisted acoustic ink printing process, the inks also are sufficiently conductive to permit the transmission of electrical signals generated by the electric field assisted acoustic ink jet printer; the inks preferably exhibit a conductivity of from about 2 to about 9 log(picomho/cm) (measured under melt conditions at about 150.degree. C. by placing an aluminum electrode in the molten ink and reading the resistivity output on a GenRad 1689 precision RLC Digibridge at a frequency of 1 kilohertz). In general, the conductivity of a material can be measured in terms of the reciprocal of resistivity, which is the capacity for electrical resistance. Further information regarding electric field assisted acoustic ink printing processes is disclosed in, for example, Copending Application U.S. Ser. No. 09/280,717, filed Mar. 30, 1999, entitled "Method and Apparatus for Moving Ink Drops using an Electric Field and Transfuse Printing System Using the Same," with the named inventors John S. Berkes, Vittorio R. Castelli, Scott A. Elrod, Gregory J. Kovacs, Meng H. Lean, Donald L. Smith, Richard G. Stearns, and Joy Roy, the disclosure of which is totally incorporated herein by reference, which discloses a method of forming and moving ink drops across a gap between a printhead and a print medium or intermediate print medium in a marking device. The method includes generating an electric field, forming the ink drops adjacent to the printhead, and controlling the electric field. The electric field is generated to extend across the gap. The ink drops are formed in an area adjacent to the printhead. The electric field is controlled such that an electrical attraction force exerted on the formed ink drops by the electric field is the greatest force acting on the ink drops. The marking device can be incorporated into a transfuse printing system having an intermediate print medium made of one or more materials that allow for lateral dissipation of electrical charge from the incident ink drops.
U.S. Pat. No. 4,751,528 (Spehrley, Jr. et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink jet system including a temperature-controlled platen provided with a heater and a thermoelectric cooler electrically connected to a heat pump and a temperature control unit for controlling the operation of the heater and the heat pump to maintain the platen temperature at a desired level. The apparatus also includes a second thermoelectric cooler to solidify hot melt ink in a selected zone more rapidly to avoid offset by a pinch roll coming in contact with the surface of the substrate to which hot melt ink has been applied. An airtight enclosure surrounding the platen is connected to a vacuum pump and has slits adjacent to the platen to hold the substrate in thermal contact with the platen.
U.S. Pat. No. 4,791,439 (Guiles), the disclosure of which is totally incorporated herein by reference, discloses an ink jet apparatus for use with hot melt ink having an integrally connected ink jet head and reservoir system, the reservoir system including a highly efficient heat conducting plate, such as aluminum, inserted within an essentially non-heat conducting reservoir housing. The reservoir system has a sloping flow path between an inlet position and a sump from which ink is drawn to the head, and includes a plurality of vanes situated upon the plate for rapid heat transfer.
U.S. Pat. No. 4,853,036 (Koike et al.) and U.S. Pat. No. 5,124,718 (Koike et al.), the disclosures of each of which are totally incorporated herein by reference, disclose an ink for ink-jet recording which comprises a liquid composition essentially comprised of a coloring matter, a volatile solvent having a vapor pressure of 1 mmHg or more at 25.degree. C., and a material being solid at room temperature and having a molecular weight of 300 or more; and prepared so as to satisfy formula B.sub.1 /A.sub.1.gtoreq.3, assuming viscosity as A.sub.1 cP at 25.degree. C. measured when the content of the solid material in said composition is 10 percent by weight, and assuming viscosity as B.sub.1 cP at 25.degree. C. measured when the content of the solid material in said composition is 30 percent by weight. An ink-jet recording process employing the above mentioned ink is also provided.
U.S. Pat. No. 5,006,170 (Schwarz et al.) and U.S. Pat. No. 5,122,187 (Schwarz et al.), the disclosures of each of which are totally incorporated herein by reference, disclose hot melt ink compositions suitable for ink jet printing which comprise a colorant, a binder, and a propellant selected from the group consisting of hydrazine; cyclic amines; ureas; carboxylic acids; sulfonic acids; aldehydes; ketones; hydrocarbons; esters; phenols; amides; imides; halocarbons; urethanes; ethers; sulfones; sulfamides; sulfonamindes; phosphites; phosphonates; phosphates; alkyl sulfines; alkyl acetates; and sulfur dioxide. Also disclosed are hot melt ink compositions suitable for ink jet printing which comprise a colorant, a propellant, and a binder selected from the group consisting of rosin esters; polyamides; dimer acid amides; fatty acid amides; epoxy resins; fluid paraffin waxes; fluid microcrystalline waxes; Fischer-Tropsch waxes; polyvinyl alcohol resins; polyols; cellulose esters; cellulose ethers; polyvinyl pyridine resins; fatty acids; fatty acid esters; poly sulfonamides; benzoate esters; long chain alcohols; phthalate plasticizers; citrate plasticizers; maleate plasticizers; sulfones; polyvinyl pyrrolidinone copolymers; polyvinyl pyrrolidone/polyvinyl acetate copolymers; novalac resins; natural product waxes; mixtures of linear primary alcohols and linear long chain amides; and mixtures of linear primary alcohols and fatty acid amides. In one embodiment, the binder comprises a liquid crystalline material.
U.S. Pat. No. 5,041,161 (Cooke et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink jet ink which is semi-solid at room temperature. The subject ink combines the advantageous properties of thermal phase change inks and liquid inks. More particularly, the inks comprise vehicles, such as glyceryl esters, polyoxyethylene esters, waxes, fatty acids, and mixtures thereof, which are semi-solid at temperatures between 20.degree. C. and 45.degree. C. The ink is impulse jetted at an elevated temperature in the range of above 45.degree. C. to about 110.degree. C., at which temperature the ink has a viscosity of about 10 to 15 centipoise. The subject inks exhibit controlled penetration and spreading, but do not remain on the surface of most substrates where they would be prone to burnishing, cracking or flaking. These inks further comprise 0.1 to 30 weight percent of a colorant system.
U.S. Pat. No. 5,111,220 (Hadimoglu et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of fabricating an acoustic ink printhead with an integrated liquid level control layer. With standard photolithographic techniques, acoustic lenses and ink supply channels are defined in a substrate. Apertures are created in a spacer layer plate to define cavities to hold the ink reservoirs for each ejector. Corresponding alignment holes are also made in the substrate and in the spacer layer plate. With spheres matching the size of the alignment holes, the spheres engage the alignment holes to precisely align the apertures in the spacer layer plate with the acoustic lenses in the substrate. The plate and substrate are then bonded for an integrated acoustic printhead with liquid level control by capillary action.
U.S. Pat. No. 5,121,141 (Hadimoglu et al.), the disclosure of which is totally incorporated herein by reference, discloses an acoustic ink printhead with an integrated liquid level control layer. A spacer layer is fixed to a substrate. Apertures are created in the spacer layer, which is then used as a mask, to define acoustic lenses and ink supply channels in the substrate. The apertures in the spacer layer used to define self-aligned acoustic lenses and to form the cavities to hold the ink reservoirs for each ejector. The thickness of the spacer layer is set so that acoustic waves from the acoustic lens below are focused at the free surface of the ink which maintains its level at the top of the spacer layer by capillary action.
U.S. Pat. No. 5,371,531 (Rezanka et al.), the disclosure of which is totally incorporated herein by reference, discloses a multi-color ink-jet printer in which a first partial image is created on a recording medium, and then a second partial image is created on the same recording medium after the first partial image is substantially dried. The first partial image comprises an ink which dries at a slower rate than that of the second partial image. In one embodiment, means are provided for heating the recording medium prior to the creation of the second partial image.
U.S. Pat. No. 5,688,312 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and an imide or bisimide with a viscosity of from about 1 centipoise to about 10 centipoise at a temperature of from about 125.degree. C. to about 180.degree. C., and which imide or bisimide is of the Formulas I or II, respectively: ##STR1##
wherein R is a hydrocarbon of from about 2 to about 50 carbon atoms; R' is an alkylene hydrocarbon or a polyalkyleneoxide, each with from about 2 to about 30 carbon atoms; and X is an arylene of from 6 to about 24 carbon atoms, or an alkylene of from about 2 to about 10 carbon atoms.
U.S. Pat. No. 5,700,316 (Pontes et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and a vehicle of a poly(alkylene oxide)-alkylate (I), a poly(alkylene oxide)-dialkylate (II), a polyoxa-alkanoate ester (III), or a polyoxa-alkanedioate diester (IV), and which ink possesses a viscosity of from about 1 centipoise to about 15 centipoise at a temperature of from about 125.degree. C. to about 165.degree. C., and which vehicle is of the formulas ##STR2##
wherein R is alkyl, R' is an alkylene, or arylene, and n is an integer of from about 2 to about 20.
U.S. Pat. No. 5,747,554 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a polyesterified-dye (I) or polyurethane-dye (II) with a viscosity of from about 3 centipoise to about 20 centipoise at a temperature of from about 125.degree. C. to about 165.degree. C. and represented by the formulas ##STR3##
wherein A is an organic chromophore, Y is an oxyalkylene or poly(oxyalkylene), R is an arylene or alkylene, n represents the number of repeating segments, and is an integer of from about 2 to about 50, and p represents the number of chains per chromophore and is an integer of from about 1 to about 6.
U.S. Pat. No. 5,844,020 (Paine et al.) and U.S. Pat. No. 5,952,402 (Paine et al.), the disclosures of each of which are totally incorporated herein by reference, disclose an ink composition comprising a colorant and a phase change vehicle derived from the reaction product of a resin containing at least one furan moiety and at least one maleimide moiety, and wherein said ink possesses a viscosity of from about 1 centipoise to about 20 centipoise at a temperature of from about 100.degree. C. to about 180.degree. C.
U.S. Pat. No. 5,902,390 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid ketone, (2) a solid ketone, (3) a lightfastness UV absorber, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 5,922,117 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (1) a liquid alcohol vehicle, (2) a solid alcohol compound, (3) a quaternary compound, (4) a lightfastness UV absorber, (5) a lightfastness antioxidant, and (6) a colorant.
U.S. Pat. No. 5,931,995 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid aldehyde, a liquid acid, or mixtures thereof, (2) a solid additive aldehyde compound, a solid additive acid compound, or mixtures thereof, (3) a lightfastness UV absorber, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 5,958,119 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (1) a liquid cyclic vehicle (2) a cyclic compound, (3) a liquid crystalline nitrile compound, (4) a lightfastness UV absorber, (5) a lightfastness antioxidant, and (6) a colorant.
U.S. Pat. No. 6,045,607 (Breton et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition containing (1) a first solid carbamate, (2) a second carbamate with a dissimilar melting point than the first solid carbamate (1), (3) a lightfastness component, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 6,066,200 (Breton et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (1) a solid urea compound; (2) an alcohol, (3) a lightfastness component; (4) a lightfast antioxidant; and (5) a colorant.
U.S. Pat. No. 6,071,333 (Breton et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition containing (1) a solid carbamate compound; (2) an alcohol compound with a melting point of from about 25.degree. C. to about 90.degree. C.; (3) a lightfastness component; (4) a lightfastness antioxidant; and (5) a colorant.
U.S. Pat. No. 5,876,492 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid ester vehicle, (2) a solid ester compound, (3) a liquid crystalline ester compound, (4) a UV absorber, (5) an antioxidant, and (6) a colorant.
U.S. Pat. No. 5,279,655 (Takazawa et al.), the disclosure of which is totally incorporated herein by reference, discloses a printer ink composition containing a triphenylmethane dye or a lake pigment derived therefrom as a coloring agent, including as the coloring agent a triphenylmethane dye having general formula (I): ##STR4##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group, R.sub.5 is an aryl group, X- is a counter ion, and ring A or ring B may be substituted by one or more substituents, provided that at least one group among R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is not methyl and in the case that R.sub.5 is p-dimethylaminophenyl, at least one of R.sub.1 and R.sub.2 and at least one of R.sub.3 and R.sub.4 are not methyl; or a lake pigment derived therefrom, in order to prevent the formation of Michler's ketone. The ink composition is used for printing media for printer such as fabric ink ribbon, ink roll, ink-retaining element, thermal transfer ink ribbon, and pressure-sensitive transfer ink ribbon.
U.S. Pat. No. 5,662,736 (Sakai et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink including at least one wax, at least one coloring material, a first resin having a softening point ranging from room temperatures to 100.degree. C., and a second resin having a softening point ranging from 50.degree. C. to 150.degree. C. and higher than the softening point of the first resin. The hot melt ink has an appropriate softening point and high light transmittance while maintaining fixing property and appropriate viscosity by combining a resin with a relatively low molecular weight and a resin with a relatively high molecular weight.
U.S. Pat. No. 5,185,035 (Brown et al.), the disclosure of which is totally incorporated herein by reference, discloses transparent hot melt jet inks including a coloring agent, a vehicle for the coloring agent including a thermoplastic nontransparent base material and a transparentizing agent containing a glycol ester of a C.sub.18-35 fatty acid, a glyceryl ester of a C.sub.18-36 fatty acid with metal soaps, a polyethylene wax having a molecular weight of 400 to 1200, a synthetic paraffin wax, or a linear alcohol with a molecular weight of 500 to 1000 or a mixture thereof, a microcrystalline or modified microcrystalline wax.
U.S. Pat. No. 6,022,910 (Nishizaki et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt solid ink composition comprising at least one polyamide and at least one terpene resin. The terpene resin is present in an amount of from 0.5 percent by weight to 15 percent by weight based on the total weight of the ink composition. This hot melt solid ink composition can be stable to heat upon recording using ink jet recording apparatus where ink is heated to melt at a temperature higher than ordinary temperature to make a record, and has a superior transparency and a superior adhesion to printing mediums.
U.S. Pat. No. 5,286,288 (Tobias et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink composition for use in continuous ink jet printing comprising an electrolyte, an electrolyte-solvating and dissociating compound, and an image-forming agent, said ink being solid at about 25.degree. C., said ink liquefying at a temperature between 75.degree. C. and 175.degree. C., and said ink in the liquid stage having a conductivity of greater than about 100 microsiemens/cm.
U.S. Pat. No. 5,378,574 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses ink jet inks and liquid developers which contain colored particles comprising hydrophilic silica particles, to the surfaces of which dyes are covalently bonded through silane coupling agents. The ink jet inks generally comprise a liquid medium and a plurality of the colored silica particles. The liquid developers generally comprise a liquid medium, a resin, a plurality of the colored silica particles, and a charge control agent. The particles are prepared by a process which comprises reacting hydrophilic silica particles with a silane coupling agent in the absence of water to form particles having covalently attached thereto coupling agents, followed by reacting a dye with the coupling agent attached to the silica particles.
U.S. Pat. No. 5,607,501 (Fujioka), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink utilizable for an ink jet printer, the hot melt ink being prepared by mixing distearyl ketone (91 parts by weight), .alpha.-olefin maleic anhydride copolymer (6 parts by weight), and 1,1,3-tris(3-tert-butyl-4-hydroxy-6-methyl)butane (1 part by weight), thereafter by adding C.I. SOLVENT RED 49 (2 parts by weight) to the obtained mixture, and by sufficiently stirring and dissolving C.I. SOLVENT RED 49 in the ink.
U.S. Pat. No. 5,954,866 (Ohta et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition for ink jet recording which can meet many property requirements for an ink composition used in ink jet recording and, in addition, can yield a good image on a recording medium having a layer comprising a water soluble resin. An ink jet recording method using the same is also provided. An ink composition comprising a pigment as a colorant, an anionic surfactant having a polyoxyethylene group, a dispersant, and water is used to record an image on a recording medium having a layer comprising a water-soluble resin by ink jet recording.
U.S. Pat. No. 5,134,189 (Matsushita et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink for heat-sensitive recording which comprises, as color developing components, an aromatic or heterocyclic isocyanate compound and an imino compound which are dispersed and/or dissolved in an organic solvent and, as a binder, (1) a copolymer of a mixture of component (a) which is an .alpha.,.beta.-ethylenically unsaturated carboxylic acid and component (b) which is at least one monomer selected from the group consisting of acrylic acid esters, methacrylic acid esters and aromatic vinyl compounds and/or (2) a three-component- or more component-copolymer, the fundamental skeleton of which is composed of isobutylene and maleic anhydride. The ink may additionally contain a heat-meltable substance and the like. The ink has a good wettability to a plastic substrate and can be dried rapidly in a printing machine.
U.S. Pat. No. 4,931,095 (Nowak et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink for hot melt ink jet printing comprising a benzoate solvent which is solid at room temperature. This ink is suitable for jetting onto an opaque substrate such as paper for directly readable print, or onto a transparent substrate, such as an acetate or polycarbonate sheet, to make a projectable transparency.
U.S. Pat. No. 5,621,447 (Takizawa et al.), the disclosure of which is totally incorporated herein by reference, discloses a jet recording method wherein a normally solid recording material is placed in a heat-melted state in a path defined by a nozzle leading to an ejection outlet and, in a recording step, is imparted with a thermal energy corresponding to a recording signal to generate a bubble, thus ejecting a droplet of the recording material out of the ejection outlet. As an improvement, in the recording step, the bubble is caused to communicate with ambience, and the droplet is ejected in a diameter d (.mu.m) and at an average speed v (m/sec) satisfying: 10.ltoreq.d.ltoreq.60 and 7.ltoreq.v.ltoreq.20. As a result, the droplet is deposited on a recording medium without pileup or scattering.
U.S. Pat. No. 5,389,133 (Gundlach et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for preparing an aqueous ink composition which comprises adjusting the pH of the ink with phosphorous acid or phosphite salts. Also disclosed are ink compositions prepared by this process. In certain preferred embodiments, the ink compositions can also contain betaine, sulfolane, dimethyl sulfoxide, or N,N'-bis(3-aminopropyl)-1,2-ethylenediamine, as well as mixtures thereof. In other preferred embodiments, the ink composition comprises an organic component selected from the group consisting of sulfolane, dimethyl sulfoxide, and mixtures thereof, and anions selected from the group consisting of phosphite, hypophosphite, phosphate, polyphosphate, sulfate, hexafluorophosphate, glycolate, acetate, ethylenediaminetetraacetate, formate, borate, sulfite, sulfamate, and mixtures thereof.
JP 6 228 476, the disclosure of which is totally incorporated herein by reference, discloses a recording liquid obtained by adding a solvent such as isopropyl alcohol, thiodiglycol, or 2-pyrrolidone and ion exchange water to at least one of phthalocyanine, xanthene, triphenylmethane, anthraquinone, monoazo, disazo, trisazo, and tetraazo-based dyes or a pigment, stirring and mixing the resultant mixture, preparing a recording liquid, and further blending the prepared recording liquid with 2-oxazolidone. The recording liquid has good humectant properties, discharge stability, and resistance of a member to the recording liquid and high solubility in dyes without causing a bronze phenomenon in printed letters, and is capable of providing clear images having high image density and useful for ink jet recording.
U.S. Pat. No. 5,270,730 (Yaegashi et al.), the disclosure of which is totally incorporated herein by reference, discloses a normally solid recording material that is heat-melted in a path defined by a nozzle leading to an ejection outlet and is imparted with a thermal energy from a heater corresponding to a recording signal to generate a bubble. As a result, a droplet of the recording material is ejected out of the ejection outlet under the action of the bubble while the bubble is caused to communicate with ambience. The normally solid recording material preferably contains a colorant, a first heat-fusible solid substance having a melting point Tm of 36.degree.-150.degree. C. and a boiling point Tb of 150.degree.-370.degree. C., and a second heat-fusible solid substance having a melting point Tm and a solidifying point Tf satisfying a relationship of Tm-Tf.ltoreq.30.degree. C. The distance between the heater and the ejection outlet, the sectional size of the nozzle and the thermal energy imparted by the heater are controlled to cause the bubble to communicate with ambience.
U.S. Pat. No. 5,053,079 (Haxell et al.), the disclosure of which is totally incorporated herein by reference, discloses a dispersed, pigmented hot melt ink containing a thermoplastic vehicle, a colored pigment, and a dispersing agent to inhibit settling or agglomeration of pigment when the ink is molten comprising an isocyanate-modified microcrystalline wax or lignite wax in an amount of 2 to 100 weight percent of the weight of the vehicle. Preferred is the isocyanate-modified microcrystalline wax marketed as Petrolite WB17.
U.S. Pat. No. 5,397,388 (Fujioka), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink for an ink jet printer comprising 50 weight percent or more of a solid wax that is solid at normal temperatures and has a solubility parameter of not larger than 9.00, an organic substance having a solubility parameter greater than that of the solid wax, a polymer material that is miscible with at least one of the solid wax and the organic substance and which has a weight average molecular weight of not less than 500, and a coloring material. The hot melt ink exhibits good dispersability and dispersion stability of the coloring material with good heat stability and color fastness to light.
U.S. Pat. No. 5,354,368 (Larson, Jr. et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt jet ink composition comprising a tall oil resin having a high acid number that exhibits improved adhesion when printed onto substrates.
While known compositions and processes are suitable for their intended purposes, a need remains for phase change inks that are suitable for hot melt ink jet printing processes, such as hot melt piezoelectric ink jet printing processes and the like. Further, a need remains for phase change inks that are suitable for hot melt acoustic ink jet printing processes. Additionally, a need remains for phase change inks that, upon cooling, form images with desirable hardness values. There is also a need for phase change inks that, upon cooling, form images that are robust and abrasion resistant. In addition, there is a need for phase change inks that form images compatible with a wide variety of print substrates, such as plain papers, coated papers, transparencies, and the like. Further, there is a need for phase change inks that form images of photographic quality, particularly when printed on plain paper. Additionally, there is a need for phase change inks that generate waterfast images. A need also remains for phase change inks that generate lightfast images. In addition, a need remains for phase change inks that generate high quality images on a wide variety of substrates, including plain paper. Further, a need remains for phase change inks that generate fast-drying images. Additionally, a need remains for phase change inks that generate high quality text images. There is also a need for phase change inks that generate high quality graphics images. In addition, there is a need for phase change inks that form images wherein the colorant is retained on the surface of the print substrate while the ink vehicle can continue to spread throughout the substrate. Further, there is a need for phase change inks that generate images with minimal feathering. Additionally, there is a need for phase change inks that exhibit minimal intercolor bleed when two inks of different colors are printed adjacent to each other on a substrate. A need also remains for phase change inks that generate images with high image permanence. In addition, a need remains for phase change inks suitable for ink jet printing processes wherein the substrate is heated prior to printing and is cooled to ambient temperature subsequent to printing (also known as heat and delay printing processes). Further, a need remains for phase change inks that can generate images of desirably high optical density values even when the inks contain relatively low colorant concentrations. Additionally, a need remains for phase change inks that, when printed onto substrates, cause minimized curling of the substrate. There is also a need for phase change inks that exhibit desirable crease resistance. In addition, there is a need for phase change inks that generate images with desirably high transparency and projection efficiency. Further, there is a need for phase change inks wherein the speculate size of spherical ink crystals formed therein during cooling and solidification can be reduced from about 6 to 9 microns to about 2 to 4 microns. Additionally, there is a need for phase change inks wherein the speculate size of spherical ink crystals formed therein during cooling and solidification can be reduced from about 6 to 9 microns to about 1 to 3 micron when the inks further contain crystallinity inhibitors derived from, for example, low viscosity unsaturated aliphatic acid compounds. There is also a need for phase change inks that, when incorporated into an ink jet printer, exhibit controlled jettability. In addition, there is a need for phase change inks that generate images with excellent projection efficiency, with no need for a post fusing step to achieve such efficiency. Further, there is a need for phase change inks that generate images with desirably high waterfastness values. Additionally, there is a need for phase change inks that generate images with desirably high lightfastness values. A need also remains for phase change inks that exhibit desirable viscosity values at hot melt ink printing temperatures. In addition, a need remains for phase change inks comprising ink vehicles in which colorants such as dyes are easily dissolved or dispersed.